Reg:

Every year there are a few reports of people struck by and often killed by
lightning.

Indeed Florida is the leading place in the whole world for lightning
activity and lightning deaths.

In Florida we have really vicious thunderstorm activity throughout the
summer months. These storms come up fast, thunderheads rising upwards of
50,000 feet, with black wall clouds decending to ground level and the air
thick with static and rain so hard that you cannot see more than 25 feet.
Impressive stuff!

I have never personally met anyone who was struck by lightning.

One of my own [arbitrary length] dipoles was simply vaporized by a strike
when I was not at home... the ladder line that fed it's center was also
missing and there was a two foot diameter hole about a foot deep in the lawn
where I had left the end of the line laying on the ground. That's where I
place the ladder line when not in the shack. When I returned home after
that storm, I found the rope ends at the two supports simply swinging in the
wind with the insulators on the ends still intact. During the annual ARRL
Field Day event, held at the peak of Florida lightning season, in June of
each year, I/we quickly disconnect feedlines and throw them well away from
the transmitter sites during thunderstorm approach, on several occasions
during those Field Days, and from a distance and under appropriate shelter,
I have personally watched arcs jumping across the air gap between the
conductors of the end of ladder line lying on the ground during the passage
of thunderclouds. But I have never witnessed an actual strike on one of
those antennas.

I don't have statistics at hand, but I can relay that most of the news
reports of lightning deaths that I recall here in Florida were of the deaths
of unfortunate golfers who failed to take shelter during a thunderstorm
approach. I do recall a news report of someone killed by lightning on a
Florida beach within the past couple of years.

It would be my guess that most who are struck by lightning in Florida are
visitors... As far as I can tell, most folks who live in Florida year round
are very well aware of the dangers of lightning and take appropriate
cautions.

--
Pete k1po
Indialantic By-the-Sea, FL


"Reg Edwards" wrote in message
...
There is much correspondence on these walls about protecting equipment
and property from lightning strikes. But there is never anything said
about protecting people. Where are your concerns?

In this country, UK, I can't remember the last time I read in the
newspaper about anybody being killed by lightning. It is extremely
rare.

It doesn't appear to give US citizens much cause for concern. Are you
all very brave? Or have you just got used to it.

Just curious. What is the annual death rate due to lightning, per head
of population, in states like Florida? Do you keep statistics?

How does it compare with the death rate from being chewed to death by
alligators in Florida swamps? Or dying from rattlesnake bites in
Arizona? Does lightning make it to the newspapers?
----
Reg.

Peter O. Brackett wrote:
Reg:

Every year there are a few reports of people struck by and often killed by
lightning.

Indeed Florida is the leading place in the whole world for lightning
activity and lightning deaths.

In Florida we have really vicious thunderstorm activity throughout the
summer months. These storms come up fast, thunderheads rising upwards of
50,000 feet, with black wall clouds decending to ground level and the air
thick with static and rain so hard that you cannot see more than 25 feet.
Impressive stuff!

I have never personally met anyone who was struck by lightning.

One of my own [arbitrary length] dipoles was simply vaporized by a strike
when I was not at home... the ladder line that fed it's center was also
missing and there was a two foot diameter hole about a foot deep in the lawn
where I had left the end of the line laying on the ground. That's where I
place the ladder line when not in the shack. When I returned home after
that storm, I found the rope ends at the two supports simply swinging in the
wind with the insulators on the ends still intact. During the annual ARRL
Field Day event, held at the peak of Florida lightning season, in June of
each year, I/we quickly disconnect feedlines and throw them well away from
the transmitter sites during thunderstorm approach, on several occasions
during those Field Days, and from a distance and under appropriate shelter,
I have personally watched arcs jumping across the air gap between the
conductors of the end of ladder line lying on the ground during the passage
of thunderclouds. But I have never witnessed an actual strike on one of
those antennas.

I don't have statistics at hand, but I can relay that most of the news
reports of lightning deaths that I recall here in Florida were of the deaths
of unfortunate golfers who failed to take shelter during a thunderstorm
approach. I do recall a news report of someone killed by lightning on a
Florida beach within the past couple of years.

It would be my guess that most who are struck by lightning in Florida are
visitors... As far as I can tell, most folks who live in Florida year round
are very well aware of the dangers of lightning and take appropriate
cautions.

--
Pete k1po
Indialantic By-the-Sea, FL


"Reg Edwards" wrote in message
...

There is much correspondence on these walls about protecting equipment
and property from lightning strikes. But there is never anything said
about protecting people. Where are your concerns?

In this country, UK, I can't remember the last time I read in the
newspaper about anybody being killed by lightning. It is extremely
rare.

It doesn't appear to give US citizens much cause for concern. Are you
all very brave? Or have you just got used to it.

Just curious. What is the annual death rate due to lightning, per head
of population, in states like Florida? Do you keep statistics?

How does it compare with the death rate from being chewed to death by
alligators in Florida swamps? Or dying from rattlesnake bites in
Arizona? Does lightning make it to the newspapers?
----
Reg.






But are the thunderclouds lumped elements or transmission lines,
peter?
73,
Tom Donaly, KA6RUH

Hi Tom:

Hmmm... Thunderclouds, lumped or distributed? It all depends upon the
application requirments... if the occurence is infrequent one may make a
quasi-static assumption and invoke DC conditions.

Then we can make an approximation and treat the lightning stroke just as a
DC conductor.

Now... Just what is the steady state DC value for a lightning stroke?

Ignoring the parasitic capacitance between strokes... we can approximate it
as a long vertical wire, without loading...

Then...

Well you get the picture [grin].

Incidently we are in a very unusual dry spell here on the barrier island off
Florida's East coast... we have only had about 1/8 inch of rain in the past
three months, and the whole County is on fire!

Regards,

--
Pete k1po
Indialantic By-the-Sea, FL

"Tom Donaly" wrote in message
. net...
Peter O. Brackett wrote:
Reg:

Every year there are a few reports of people struck by and often killed
by lightning.

Indeed Florida is the leading place in the whole world for lightning
activity and lightning deaths.

In Florida we have really vicious thunderstorm activity throughout the
summer months. These storms come up fast, thunderheads rising upwards of
50,000 feet, with black wall clouds decending to ground level and the air
thick with static and rain so hard that you cannot see more than 25 feet.
Impressive stuff!

I have never personally met anyone who was struck by lightning.

One of my own [arbitrary length] dipoles was simply vaporized by a strike
when I was not at home... the ladder line that fed it's center was also
missing and there was a two foot diameter hole about a foot deep in the
lawn where I had left the end of the line laying on the ground. That's
where I place the ladder line when not in the shack. When I returned
home after that storm, I found the rope ends at the two supports simply
swinging in the wind with the insulators on the ends still intact.
During the annual ARRL Field Day event, held at the peak of Florida
lightning season, in June of each year, I/we quickly disconnect feedlines
and throw them well away from the transmitter sites during thunderstorm
approach, on several occasions during those Field Days, and from a
distance and under appropriate shelter, I have personally watched arcs
jumping across the air gap between the conductors of the end of ladder
line lying on the ground during the passage of thunderclouds. But I have
never witnessed an actual strike on one of those antennas.

I don't have statistics at hand, but I can relay that most of the news
reports of lightning deaths that I recall here in Florida were of the
deaths of unfortunate golfers who failed to take shelter during a
thunderstorm approach. I do recall a news report of someone killed by
lightning on a Florida beach within the past couple of years.

It would be my guess that most who are struck by lightning in Florida are
visitors... As far as I can tell, most folks who live in Florida year
round are very well aware of the dangers of lightning and take
appropriate cautions.

--
Pete k1po
Indialantic By-the-Sea, FL


"Reg Edwards" wrote in message
...

There is much correspondence on these walls about protecting equipment
and property from lightning strikes. But there is never anything said
about protecting people. Where are your concerns?

In this country, UK, I can't remember the last time I read in the
newspaper about anybody being killed by lightning. It is extremely
rare.

It doesn't appear to give US citizens much cause for concern. Are you
all very brave? Or have you just got used to it.

Just curious. What is the annual death rate due to lightning, per head
of population, in states like Florida? Do you keep statistics?

How does it compare with the death rate from being chewed to death by
alligators in Florida swamps? Or dying from rattlesnake bites in
Arizona? Does lightning make it to the newspapers?
----
Reg.






But are the thunderclouds lumped elements or transmission lines,
peter?
73,
Tom Donaly, KA6RUH

In article . net,
Peter O. Brackett wrote:

But are the thunderclouds lumped elements or transmission lines,
peter?

Hmmm... Thunderclouds, lumped or distributed? It all depends upon the
application requirments... if the occurence is infrequent one may make a
quasi-static assumption and invoke DC conditions.

I suspect that they're more correctly modelled as resonant circuits...
specifically, as quartz-crystal oscillators.

I keep hearing pilots talk about "clouds full of rocks"...

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Peter O. Brackett wrote:

Hi Tom:

Hmmm... Thunderclouds, lumped or distributed? It all depends upon the
application requirments... if the occurence is infrequent one may make a
quasi-static assumption and invoke DC conditions.

Then we can make an approximation and treat the lightning stroke just as a
DC conductor.

No!! A much better model is a capacitor arcing over. The current in the
strike goes from zero to Imax [100,000 amperes] in less than 1
microsecond. This is followed by a decaying current [approximate
exponential decay] that reaches 'steady state' in several 10s of
milliseconds. This is followed by an secondary exponential decay of up
to 500 milliseconds at somewhere around 500 to 600 amperes [this is
basically the sustaining or continuing channel current.

The static we hear is caused by the displacement current in the initial
discharge. The bandwidth of the static is determined by the rise and
fall times of the initial discharge characteristics.


Now... Just what is the steady state DC value for a lightning stroke?

90% of all lightning strikes in the USA have a "continuing channel
current" [long term channel current] of less than 600 amperes. It
continues for less than 1 second.


Ignoring the parasitic capacitance between strokes... we can approximate it
as a long vertical wire, without loading...

Balanced SNIPPED